This invention relates to the plastic metal working, particularly to tube rolling production and can be applied for tube cold pilgering on rolling machines.
Realization of efficient deformation scheme of rolling procedure providing stability of physical-mechanical parameters and geometrical dimensions of rolled stock is considerably defined by quality of manufacturing of working surfaces of shaping tools, smoothness of its working parts cojugation and potentialities of machine equipment to reproduce the real shape of working surface which is at most approached to the shape of calculated curve.
Available is pilger tooling consisting of mill rollers, with ridge of roll passes executed in parabola, and mandrel of decreasing cross section with parabolic generatrix, whereupon the ridge of roll pass has parabolic factor, a unit higher than the factor of mandrel generatrix parabola (Inventor""s Certificate of USSR No. 534261, International Classification B 21 B 21/02, I.E. No. 41, 1976).
Available is pilger tooling including tapered mandrel and pilger rollers with roll pass having along the length of evolvement the reduction zone, the swaging zone with inclination angle of its genetrix to the mandrel axis greater than the inclination angle of mandrel genetrix, the pre-conditioning zone and the calibrating zone. Therewith the genetrix of the pre-conditioning zone has the inclination angle to the mandrel axes composing 0,5-0,9 of the inclination angle of mandrel genetrix, and the length of the pre-conditioning zone composes 0,3-0,6 of the length of the swaging zone (Inventor""s Certificate of USSR No. 822937, International Classification B 21 B 21/02, 1.B. No. 15, 1981).
Available is pilger tooling for Zircalloy cladding tubes ( S. Reschke, A. Schaa und T. Grimmelsmann xe2x80x9cVERBESSERUNG DES HERSTELLUNGSVERFAHRENS FUR ZIRCALOY- HULLROHRExe2x80x9d. Metall, 1986, H. No. 4, S.338-346.), characterized by the following:
the beginning of the ring die has the zone of weak reduction:
the maximum deformation occurs in the first half of evolvement;
the angle of taper at the end of the working section is minimum (0,04 mm per 10 degrees of roll barrel perimeter).
As appears from the text that when using these tools it is not totally possible to avoid the formation of small tube defects.
The most close technical decision to the claimed is design of pilger tooling in which the evolvement of calibration of the external and profile of the internal tool have the shape of constantly concave, mainly parabolic curve along the whole working length.
In this case:
the constant, mainly parabolic curve of internal tool and the evolvement of external tool are described by one and the same mathematical function and posses identical parabolic numbers:
curve entry into calibrating section is carried on tangentially and overlaps cylindrical and tapered main shape (FRG Patent No. 1777043, 1971).
The geometry of parabolic curves of internal and external tools does not depend on physical-mechanical properties of rolled material. Constantly concave shape of evolvement of external and internal profile of tools along its total working length complicates formation of tapered tooling or internal tooling of another shape ( Z. A. Koff, P. M. Soloveytchik, V. A. Aljoshin, M. I. Grishpun xe2x80x9cTube Cold Pilgeringxe2x80x9d. Metallurgizdat. Sverdlovsk. 1962. Glen Stapleton xe2x80x9cCOLD PILGER TECHNOLOGYxe2x80x9d. 1683 W.216th Street. USA. 1996).
The claimed invention solves the problem with improvement of geometrical dimensions accuracy and surface quality, stability of mechanical properties and decreasing of tubes"" defectness.
The purpose in hand is obtained by creation of the best deformation schemes of the tube billet by means of applying working tools design calculated with regard to metal physical-mechanical properties and rolling schemes of the tube billet.
Technical result is attained by the fact that in contrast to the known design of tool made in the form of external and internal shape-forming tools, profiled along the working length in the form of parabolic curves, created on base of mathematical calculations,xe2x80x94geometry of curves of evolvement of profile of external tool and profile of internal tool is generated by key points of various spline-functions (I. N. Bronshtein, K. A. Semendjaev xe2x80x9cHandbook in mathematicsxe2x80x9d. Moscow. Nauka. 1986. Page 504. K. De Bor xe2x80x9cSpline practical manualxe2x80x9d. Moscow. Radio and Communication. 1985.)
Technical result is attained also by the fact that on each stage of rolling design of each separate external or internal tool is carried out in the form of unified curve. This allows to automate the process of manufacturing of tool profiles (to use, for example, CNC).
The existing processes of manufacturing of shape-forming profiles of tools for tube cold pilgering, plotted according to calculated curves of the second and higher factors do not provide the ideal smooth transition in the points of their mutual conjugation.
Application of spline-functions for calculation made it possible to provide transition smoothness on processed surfaces in indicated points on the existing equipment.
Since spline-function with factor k with key-points sequence t appears to be any linear combination of B- splines with factor k for key-points sequence t (S k, t), choosing the quantity and sequence oft allows to combine the preferable smoothness level in break point with amount of key-points in this point. For all that the less quantity of key-points corresponds to the greater number of continuity conditions.
To provide stability of physical-mechanical properties of rolled tubes, when calculating the key points of curves as calculating parameters of spline-functions, along with geometrical parameters there are used factors considering physical-mechanical properties of rolled metal, for example, modulus of elasticity, yield strength, friction factor, and also rolling schemes: strain rate by wall thickness and tube inner diameter, volume of feed, etc.